I second that heavier weight for the Hobie 18. The Prindle 18 weighed 330 lbs. No boards, no dagger wells, and lighter mast, hulls, tramp, and boom.

It's pretty easy to weigh the boats. Just get two bathroom scales, load the boat with all rigging, mast, boom, sails, rudders, and blocks, and balance the boat on the scales centered under each hull on a flat surface, then add the two together.